Methods and devices for re-routing MPLS traffic

ABSTRACT

Multi-Protocol Label Switched (MPLS) traffic is re-routed to an alternate, Label Switched Path (LSP) to bypass a failure along a primary LSP, even though the failure occurs at or along an ingress section of an LSP, while associating an original IP address to the alternate path. Failures are also detected farther downstream outside an ingress section. When this occurs, MPLS traffic is re-routed to an alternate LSP which maintains the same quality of service as an original primary path and includes other network devices which are not a part of the primary path (except for the network device and a destination network device). The techniques require less resources than existing techniques.

BACKGROUND OF THE INVENTION

A Multi-Protocol Label Switched (MPLS) network is a communicationnetwork made up of a plurality of network devices which transfer orforward packets of information using so-called virtual connectionsreferred to as “label switched paths” (LSPs). Each MPLS network devicemay be a router, switch, or other device that is capable of processingpackets in accordance with MPLS standards and the like.

A conventional LSP begins at a source network device, passes throughintermediate network devices and ends at a destination network device.

If a failure at a network device or link (failure point) occursdownstream of a source network device, so-called MPLS “Fast Re-routing”is employed to bypass the failure point.

Existing MPLS Fast Re-route techniques rely on the use of MPLSforwarding tables to re-route traffic traversing a primary path to analternate path provided a failure point does not occur at an ingressregion of the primary path (i.e., along an outgoing link associated witha source network device or at a network device which neighbors thesource network device, a so-called neighboring device), where suchtables are of little use. Still further, there is no guarantee that theresultant alternate LSPs will have the same quality of service as anoriginal, primary LSP.

SUMMARY OF THE INVENTION

The present invention re-routes traffic from a primary LSP to analternative path while maintaining the same Internet Protocol (IP)address as the primary LSP even when a failure occurs at or along aningress section of the LSP. Advantageously, less resources than existingtechniques are required by making use of forwarding tables that includeIP and MPLS routing information.

In one embodiment of the invention, a network device initially routestraffic along a primary path associated with an original IP address. Atsome point in time the device detects a failure at or along an ingressregion of the path, and re-routes traffic from the primary path to analternate path using forwarding tables which include IP and MPLS routinginformation while associating the original IP address to the alternatepath. Once the failure is removed or otherwise corrected, the deviceallows traffic to once again travel along the original primary path.

In another embodiment of the invention, a network device receives afailure message from another device that has detected a failure which isnot along an ingress section. Upon receiving the message, the networkdevice re-routes traffic from a primary path to an alternate path usingforwarding tables which include IP and MPLS routing information while,again, maintaining the original IP address. In this embodiment, thealternate path maintains the same quality of service as the primary pathand includes other network devices which are not a part of the primarypath (except for the network device and a destination network device).As before, once the failure has been corrected, the network deviceallows traffic to once again travel along the original primary path.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention are described below inconjunction with the accompanying drawings in which:

FIG. 1 is a simplified block diagram of an MPLS network which includeselements capable of re-routing traffic upon detection of a failureaccording to embodiments of the present invention;

FIG. 2 is another simplified block diagram of an MPLS network whichincludes elements capable of re-routing traffic upon detection of afailure according to yet another embodiment of the present invention;

FIGS. 3A and 3B depict simplified flow diagrams of technique(s) forsetting up alternate LSPs to re-route traffic upon detection of afailure according to embodiments of the present invention;

FIG. 4 is a simplified block diagram showing an MPLS network whichincludes elements capable of re-routing traffic upon detection of afailure in accordance with techniques envisioned by the presentinvention;

FIG. 5 is a simplified flow diagram depicting the detection of a failureand the sending of a failure notification according to yet anotherembodiment of the present invention; and

FIG. 6 is a simplified flow diagram depicting the re-routing MPLStraffic upon receiving a failure notification according to yet anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention re-routes traffic around a failureusing “Ingress Protection” and/or “Full LSP Backup Protection” whileproviding the same IP address.

Ingress Protection

Ingress Protection overcomes shortcomings of MPLS Fast Re-routing byenabling the re-routing of traffic from a primary LSP if a failure pointoccurs in an ingress region, for example, along the link between thesource network device 110 and neighboring network device 120 shown inFIG. 1 or at the neighboring network device 120 shown in FIG. 2.

FIG. 1 depicts an LSP 101 made up of network devices 110-160 (andinterconnections there between) as part of an MPLS system 105.

In one embodiment of the present invention, traffic is re-routed fromthe primary path 110-160 to an alternate path 110, 180, 170, and 130 tobypass a failure (indicated by “X”) along the primary LSP 110-160.

Source network device 110 acts as an initiating network device and isoperable to route Internet Protocol (IP) packet traffic associated withan original IP address.

When the failure occurs, the initiating network device 110 eitherdetects the failure or receives a failure message from a device locateddownstream, close to the failure point, X. In response to the failure,the initiating network device 110 is yet further operable to re-routetraffic from the primary path to the alternate path using forwardingtables which include IP and MPLS routing information while reassociatingthe IP address with the alternate LSP. Reassociating the IP addressimproves the speed of re-routing because an IP routing table located(typically) in the initiating network device need not be modified which,in turn, reduces so-called packet loss. Once the failure has beencorrected, the initiating network device 110 is further operable toallow traffic to once again travel along the original primary path110-160.

As previously mentioned, the initiating network device 110 re-routestraffic along an alternate path upon detecting a failure or receiving afailure notification. The alternate path includes network devices andlinks that are not a part of the original primary path, with theexception of the starting and ending devices of the alternate LSP. Thisallows packets to bypass failed links and network devices.

FIG. 2 illustrates another type of failure which can be bypassed usingthe present invention. In FIG. 2, a failure is located at theneighboring network device 120, instead of along a neighboring linkconnecting network devices 110 and 120 as in FIG. 1. Even though thefailure occurs at a neighboring network device 120, the sametechnique(s) described with regard to FIG. 1 above may be used to bypasssuch a failure.

FIG. 3A shows a simplified flow diagram of a technique for setting up analternate LSP while FIG. 3B is a simplified flow diagram of a techniquefor updating an IP forwarding table associated with a primary andalternate LSP according to an embodiment of the invention.

Before presenting an explanation of the technique(s) depicted in FIGS.3A and 3B, it should be understood that these techniques may beimplemented in hardware, software or firmware (e.g., by programming acontrol processing section of an initiating network device like networkdevice 110) or in some combination of the three.

Beginning with FIG. 3A, step 310, a control processing section or thelike is operable to setup an alternate LSP. In the present example, theinitiating network device is the source network device 110. Aftersetting up the alternate path, forwarding information must be added toan IP forwarding table. If there exists a forwarding entry for theprimary LSP, the same information is again used as an entry for thealternative LSP. Creating and maintaining the IP forwarding table is theresponsibility of the control processing section. Updating the IPforwarding table allows the alternate and primary LSPs to share the sameaddress (e.g., IP address) so that an address reassociation may occurbetween the two when traffic switched from one or the other. Morespecifically, in step 320, the control processing section is operable todetermine whether there is an entry in a forwarding table for a primaryLSP. If not, the processing continues to step 340. If so, processingcontinues to step 330 where a new table entry is added for an alternateLSP. Next, in step 340, the control processing section is furtheroperable to associate the original address to the primary LSP and thealternate LSP.

Referring now to FIG. 3B, step 370, a request is locally generated inthe initiating network device, and is received by a forwarding sectionto update an IP forwarding table. After the request has been received,an entry associated with an LSP is added to the forwarding table, step375. In step 380, the processing section reviews the entries in theforwarding table to determine if there is an alternate LSP associatedwith the primary LSP. If there isn't, the process continues to step 395.If there is, a new alternate LSP entry is added to the forwarding tablein step 385. The process continues to step 390 where the processingsection is operable to associate the original address with both theprimary and alternate LSP. Once the original address is shared, theprocess ends at step 395.

The examples accompanying FIGS. 1-3A and B, depict the creation and useof a so-called “detour” alternate path. However, an “end-to-end”alternate path may alternatively be created, as described below.

Full LSP Backup Protection

Full LSP Backup Protection involves setting up an end-to-end alternateLSP, detecting a failure, and switching traffic to the end-to-endalternate LSP. Unlike detour alternate paths used in Ingress Protection,end-to-end alternate LSPs are configured to maintain the same quality ofservice as a primary LSP. Full LSP Backup Protection techniques may beinvoked or otherwise combined with the Ingress protection techniqueabove.

FIG. 4 is a simplified block diagram of a MPLS network 205 configured tosupport Full LSP Backup Protection techniques according to an embodimentof the invention.

In the example shown in FIG. 4, a failure occurs along a primary path,between the network devices 130 and 140. In this case, a network deviceclose to the failure (e.g., network device 130) is operable to detectthe failure. Upon detecting the failure device 130 is further operableto send a failure notification message or the like to the source networkdevice 110 which is acting as an initiating device. Upon receiving themessage, the initiating network device 110 is operable to re-routetraffic from the primary path to an end-to-end alternate path110,170,180,190 and 160 while reassociating the original IP address tothe alternate path.

With the exception of the source network device 110 and destinationnetwork device 160, none of the intermediate network devices 120-150from the original primary path are used in the end-to-end alternatepath. Such a path can be referred to as a “disjointed” path.

As their name implies, end-to-end alternate paths provide end-to-endprotection against failure and help to preserve the same quality ofservice associated with the primary LSP. Compared to MPLS FastRe-routing, end-to-end alternate LSPs provide several advantagesincluding those now described.

MPLS Fast Re-routing can be inefficient. For example, MPLS FastRe-routing creates multiple, alternate paths when there are multiplefailures along a primary LSP. This takes up a lot of resources.Moreover, to prepare in advance for a failure along a primary path, MPLSFast Re-routing presets multiple, overlapping alternate paths to protectagainst any failure on the primary path. This, too, takes up a lot ofresources. Full LSP Backup Protection, on the other hand, sets up singleend-to-end alternate paths that are disjoint from the primary path. Bybypassing all intermediate network devices in the primary path, only onealternate path is needed when one or multiple failure points occur, thusminimizing the amount of resources used.

MPLS Fast Re-routing is also deficient because it does not ensure thatthe quality of service associated with a primary LSP is maintained by analternate LSP. Full LSP Backup Protection techniques, on the other hand,use end-to-end alternate LSPs that maintain the same quality of serviceas the primary path. To help maintain the quality of service, a controlprocessing section or the like configures end-to-end alternate LSPswhich only include network devices that can maintain the same quality ofservice required by the primary LSP for which the end-to-end alternateLSP is being used as a backup LSP. The quality of service may be relatedto a service's desired bandwidth, delay, delay jitter, packet loss rate,and the like.

In addition to providing the above advantages, devices implementing FullLSP Backup Protection can be configured to allow traffic to once againtravel along a primary path once a failure has been corrected. Thisallows resources to be freed up so they can be used in anotherend-to-end alternate path.

In a further embodiment of the invention, each of the network devices inFIG. 4 may be operable to send a failure message back to a sourcenetwork device.

FIG. 5 depicts a flow diagram of some aspects of a Full LSP BackupProtection technique in greater detail. It should be understood thatsuch techniques may, for example, be implemented in hardware, software,firmware or some combination of the three in a control processingsection or the like of an intermediate network device (e.g., device 130)located close to a failure point. Beginning with step 510 the controlprocessing section is operable to detect a failure along a link orinterface making up a part of a primary path. At step 520, the controlprocessing section is operable to determine whether it is a part of asource network device or an intermediate network device. If the controlprocessing section is a part of (or co-located with) a source networkdevice, the failure event is sent locally, the current process ends(step 550), and the process of FIG. 6 begins. If the control processingsection is not a part of a source network device for the given primarypath, the control processing section is further operable to generate afailure message and to send it on to a source network device. At thispoint, the current process ends (step 550) and the process depicted bythe techniques shown in FIG. 6 are begun.

Referring now to FIG. 6, there is shown another simplified flow diagramof a Full LSP Backup Protection technique of the present invention. Asbefore, the steps shown in FIG. 6 may be implemented in hardware,software, firmware, or some combination of the three, for example, in acontrol processing section of a source network device. Beginning at step610, a control processing section is operable to receive a failuremessage from a downstream network device local to the failure point. Thefailure message is used by the control processing section to determinewhether a failure is present. The control processing section is thenoperable to determine if an alternate LSP path exists by checking thestate of the alternate network devices at step 620. If an alternate LSPdoes exist processing continues to step 670. If an alternate LSP doesnot exist, a routing manager is queried to identify an end-to-endalternate LSP. The routing manager is operable to determine anend-to-end alternate LSP disjoint from the primary LSP with the samequality of service as the primary LSP. Once an end-to-end alternate LSPhas been identified, the control processing section is operable to senda path message to downstream network devices in the alternate LSP to setup the end-to-end alternate LSP (step 630). The path message includesquality of service information and alternate LSP information. When thecontrol processing section of the source network device 110 receives aconfirmation message, e.g., RESV message used in ReSerVationProtocol—Traffic Engineer (RSVP-TE) signaling, from the downstreamnetwork devices in the end-to-end alternate LSP (step 640), the controlprocessing section is operable to add a new entry in a forwarding tablecorresponding to the primary LSP, step 650. Once the entry has beenadded, traffic is then switched to the alternate LSP (step 670), and theprocess ends (step 680).

As indicated above, a control processing section or the like may be usedto implement the embodiments discussed above. The control processingsection may be implemented using hardware, software, firmware, or somecombination of the three. In one embodiment of the present invention, acontrol processing section is operable to send and receive MPLS trafficto and from MPLS network devices. In addition to the functions alreadydescribed above, the control processing section is operable to addlabels to MPLS packets, to set up traffic paths or to update routinginformation for an MPLS network, and to monitor traffic paths todetermine if a failure has occurred. The control processing section maybe implemented on several platforms and may comprise one or more of thefollowing: an MPLS module, routing manager, RSVP-TE module, a linkmanager, and a connection manager operable to carry out the functionsdescribed throughout this description.

It has been noted that the embodiments of FIGS. 1-6 may be implementedin hardware, software, firmware and the like. These implementations maycomprise a combination of processor(s) and article(s) of manufacture,such as storage media and executable computer program(s), for example.The executable computer program(s) may comprise instructions to performthe above described functions and operations. The computer executableprogram(s) may also be provided by, or as a part of, an externallysupplied propagated signal(s) either with or without a carrier wave(s).

The discussion above describes various exemplary embodiments of thepresent invention. Variations of the examples given above may be derivedwithout departing from the spirit or scope of he present invention. Forexample, Ingress Protection techniques may be combined with Full LSPBackup Protection techniques to re-route MPLS traffic. It is next toimpossible, however, to present each and every possible variation orexample of the present invention. Rather, the scope of the invention isdetermined by the claims which follow. The following claims should beaccorded the broadest interpretations possible to cover anymodifications or equivalent structures while at the same time retainingthe claimed inventions validity.

1. A network device, wherein the device: detects a failure along aningress region of a primary path; re-routes traffic from the primarypath associated with an original Internet Protocol (IP) address to analternate path which includes the device using a forwarding table thatincludes IP and Multi-Protocol Label Switched (MPLS) routing informationwhile associating the original IP address to the alternate path upondetection of the failure; and allows traffic to travel along the primarypath when the failure is no longer detected along the ingress region. 2.The device of claim 1 wherein, the device is a multi-protocol labelswitched (MPLS) device and the primary and alternate paths are labelswitched paths (LSPs).
 3. The device of claim 1 wherein the failure isat a neighboring network device or along a link between the device andthe neighboring network device.
 4. A network device, wherein the device:receives a failure message; re-routes traffic from a primary pathassociated with an original IP address to an alternate path using aforwarding table that includes IP and MPLS routing information, saidrerouting maintaining the original address, the alternate pathcomprising devices which maintain a same quality of service as theprimary path and are not a part of the primary path except for thenetwork device and a destination network device; and allows traffic totravel along the primary path when the failure is no longer detected. 5.The device of claim 4 wherein, the network device is a MPLS device andthe primary and alternate paths are LSPs.
 6. The device of claim 4wherein, the quality of service is associated with at least one of theset consisting of bandwidth, delay, delay jitter, and packet loss rate.7. A method for re-routing traffic comprising the steps of: detecting afailure along an ingress region of a primary path; re-routing trafficfrom the primary path associated with an original IP address to analternate path which includes a source device using a forwarding tablethat includes IP and MPLS routing information while associating theoriginal address to the alternate path upon detection of the failure;and allowing traffic to travel along the primary path when the failureis no longer detected along the ingress region.
 8. The method of claim 7wherein the primary and alternate paths are LSPs.
 9. The method as inclaim 7 wherein the failure is at a neighboring network device or alonga link between the initiating device and the neighboring network device.10. A method for re-routing traffic comprising the steps of: receiving afailure message; after said receiving step, re-routing traffic from aprimary path associated with an original IP address to an alternate pathusing a forwarding table that include IP and MPLS routing information,said rerouting maintaining the original address, the alternate pathcomprising devices which maintain a same quality of service as theprimary path and are not a part of the primary path except for aninitiating network device and a destination network device; and allowingtraffic to travel along the primary path when the failure is no longerdetected.
 11. The method of claim 10 wherein the primary and alternatepaths are LSPs.
 12. The method of claim 10 wherein, the quality ofservice is associated with at least one of the set consisting ofbandwidth, delay, delay jitter, and packet loss rate.
 13. A networkdevice comprising: means for detecting a failure along an ingress regionof a primary path; means for re-routing traffic from the primary pathassociated with an original IP address to an alternate path whichincludes the device using a forwarding table that includes InternetProtocol (IP) and Multi-Protocol Label Switched (MPLS) routinginformation while associating the original IP address to the alternatepath upon detection of the failure; and means for allowing traffic totravel along the primary path when the failure is no longer detectedalong the ingress region.
 14. The device of claim 13 wherein the deviceis a MPLS device and the primary and alternate paths are LSPs.
 15. Thedevice of claim 13 wherein the failure is at a neighboring networkdevice or along a link between the device and the neighboring networkdevice.
 16. A network device comprising: means for receiving a failuremessage; means for re-routing traffic from a primary path associatedwith an original IP address to an alternate path using a forwardingtable that includes IP and MPLS routing information, said means forre-routing maintaining the original address, the alternate pathcomprising devices which maintain a same quality of service as theprimary path and are not a part of the primary path except for thenetwork device and a destination network device; and means for allowingtraffic to travel along the primary path when the failure is no longerdetected.
 17. The device of claim 16 wherein, the network device is aMPLS device and the primary and alternate paths are LSPs.
 18. The deviceof claim 16 wherein, the quality of service is associated with at leastone of the set consisting of bandwidth, delay, delay jitter, and packetloss rate.
 19. A source network device, wherein the device: detects afailure along an ingress region of a primary path, where the ingressregion comprises a link associated with the source network device;re-routes traffic from the primary path associated with an originalInternet Protocol (IP) address to an alternate path which includes thedevice using a forwarding table that includes IP and Multi-ProtocolLabel Switched (MPLS) routing information while associating the originalIP address to the alternate path upon detection of the failure; andallows traffic to travel along the primary path when the failure is nolonger detected along the ingress region.
 20. The device of claim 19wherein, the device is a multi-protocol label switched (MPLS) device andthe primary and alternate paths are label switched paths (LSPs).
 21. Thedevice of claim 19 wherein the link associated with the source networkdevice is an outgoing link or a link between the source network deviceand a neighboring network device.
 22. A source network device, whereinthe device: detects a failure along an ingress region of a primary path,where the ingress region comprises a link associated with the sourcenetwork device, and the link comprises either an outgoing link or a linkbetween the source network device and a neighboring network device;re-routes traffic from the primary path associated with an originalInternet Protocol (IP) address to an alternate path which includes thedevice using a forwarding table that includes IP and Multi-ProtocolLabel Switched (MPLS) routing information while associating the originalIP address to the alternate path upon detection of the failure; andallows traffic to travel along the primary path when the failure is nolonger detected along the ingress region.
 23. The device of claim 22wherein, the device is a multi-protocol label switched (MPLS) device andthe primary and alternate paths are label switched paths (LSPs).